The task of engineering a WDM network consists of identifying the appropriate type of equipment, the appropriate location of the equipment, and specifying the required settings of the equipment so that optical signals transmitted through the network have satisfactory optical characteristics. Computer modeling software can be used to aid in engineering new WDM networks and modifying existing WDM networks. As shown in FIG. 1, central to the engineering process is a software modeling environment 10, including a computer system 12 for running the computer modeling software. A network designer executes the software to generate a computer model 16 of an optical network 14. The optical network 14 typically includes fiber optic links 18, or optical spans, through which multiple channels of bi-directional optical signals are multiplexed on a pair of optical fibers. Each signal is defined on a carrier wavelength. The links 18 connect sites 22 in the optical network 14. A site, as used herein, generally refers to a building or structure in which network equipment and components are maintained and operated. Network equipment and components include, for example, optical amplifiers, regenerators, band equalizers, optical multiplexers, and the like.
The software modeling environment 10 allows a network designer to add, remove and/or relocate network components, and simplifies the process of changing equipment settings and topologies. Further, the software modeling environment 10 can include an analysis module for evaluating the operational parameters describing the modeled network 16 and determining their effect on the performance of the optical network 14.
When designing an optical network, a network engineer performs several general tasks. First, the engineer produces a network plan that includes a description of the functionality to be provided by the network and identifies the constraints for the network. Next, the engineer generates an initial configuration for the network. To evaluate the performance of the initial configuration, the engineer uses the analysis module to evaluate various parameters that represent the characteristics of the spans in the network. Such parameters include optical power, optical signal-to-noise ratio (OSNR), chromatic dispersion, polarization mode dispersion (PMD), jitter and crosstalk. If any of the parameters are unsatisfactory, the engineer modifies the network by changing the initial configuration, for example, by adding, removing and/or repositioning network components. After “manually” implementing the configuration modifications, the engineer again analyzes the performance of the optical network. This iterative process of manual modifications and subsequent analysis continues until an acceptable network configuration is achieved, or until it is determined that no satisfactory network configuration is possible and the design process is terminated.
The iterative process of manual modifications and analysis is complicated, time consuming and requires highly trained engineers. Consequently, the process is expensive. Moreover, because the process depends on the individual expertise and bias of the network engineers, the network configurations resulting from similar analyses are often inconsistent. The process is complex even for small networks because modifying a single network component can cause numerous changes to optical signal parameters on the connected links or on other links in the network. For example, optical amplifiers are used to extend the range of an optical signal by increasing the signal power, however, optical amplifiers increase the amplified spontaneous emission (ASE) noise of the signal. The ASE noise can be addressed by using equalization techniques, however, additional noise and optical power problems can arise.
What is needed are a system and method for designing WDM networks that overcome the cost, complexity, and time disadvantages of the current techniques.